This invention relates to a mine roof support and more particularly to a mine roof support suitable for use in a special way of mining coal, referred to as sub-level caving.
Mine roof supports include a ground engaging base section, a roof engageable canopy and hydraulic prop means for raising and lowering the canopy relative to the base section. Known roof supports for inter alia sub-level caving also include a shield section which is pivotally connected at one end to one end of the canopy and which is pivotally connected at its other end to one or more members, typically links of a lemniscate linkage arrangement, connected to the ground engaging base section. The shield section of known roof supports for sub-level caving is also provided with an opening which is normally closed by a door, but which, when the door is opened at an appropriate moment, is large enough to permit material which has fallen onto the shield section from above (e.g. by caving of a roof or, if necessary, by shot-firing) to pass through the opening into the space below that opening. In early designs of roof support for sub-level caving, the door was slidable relative to the shield section and material falling through the opening in the shield section was customarily removed by a conveyor supported on the ground engageable base section.
The conveyor for removing material falling through the opening was additional to the mine face conveyor and, in an attempt to do away with the need for this additional conveyor, later designs of roof support for sub-level caving utilised a pivotable door which when open served as a chute to guide the material from above the shield section onto the mine face conveyor.
However, it has been found that these roof supports suffer from the drawback that the angle of inclination of the chute is sometimes too small and the material does not pass along the chute.